A Broadcaster will by default use an ExecutorService, and the number of Threads will be computed
based on the number of cores/CPUs of the OS under which the application runs. Thus invoking
broadcast(Object) will be executed asynchronously so this is
important to wait for the Future.get() to awake/unblock to be guaranteed that the operation has completed.

resumeAll

releaseExternalResources

void releaseExternalResources()

Release external resources associated with this Broadcaster. This is useful when a Broadcaster no longer have
suspended AtmosphereResource and some resource (like database connections, JMS queue, etc.) needs to be
closed.